Creation of differencing disk created from earliest checkpoint

[brettski]

If the VM you are using for test kitchen has checkpoints set when the differencing disk is created it is done from the earliest checkpoint. I am assuming it using the vhdx file regardless if there are avhdx files.

New-Vhd will not create a differencing disk from an .avhdx file (it complains about the file extension). If the extension is rename from .avhdx to .vhdx then New-Vhd will create a new differencing disk from the parent.

I was hoping we could simply provide the current checkpoint's disk as the parent_vhd_name. If there is no way around not being able to create a differencing disk from a .avhdx file then it may need to be renamed first if used with kitchen::Hyperv